| dc.description.abstract | Black phosphorous (BP) also known as phosphorene is a novel two-dimensional material with a hexagonal honeycomb structure, similar to graphene where the lamellar layers are bonded to each other by Van der Waals forces. In 2014, it was obtained from the bulk black phosphorus by mechanical exfoliation method. While there is no band gap in graphene and a direct bandgap of 1.2 eV -1.8 eV in monolayer molybdenum disulfide (MoS2), the BP on the other hand, has a thickness-dependent direct bandgap ( 0.3 eV for multilayers to 2.0 eV for monolayer). BP can be efficiently applied to electronic components as it has a high on-off ratio of 104-105, and carrier mobility of ~1000 cm2V-1S-1, both of which are excellent features necessitated in logic devices. However, BP has the disadvantage of being easily oxidized in ambient conditions, resulting in the deterioration of its intrinsic electrical transport properties.
In the present study, several techniques have been explored using various passivated materials to protect BP, such as fluorinated polymer self-assembly, fluoride spin coating, and transferring of graphene to BP. Raman analysis showed that the Nafion solution can provide a long-term stability protection to BP, passivate the BP surface in an essential state, and reduce environmental degradation up to 160 days. In addition, atomic force microscopy (AFM) image shows that the Nafion solution can also remove the BP surface impurities. We also explored the chemical modification of Nafion solution on BP and its effect in electrical properties. The Nafion coating is found to enhance the electrical property of BP (on-off ratio) which may be due to the strong interaction between the BP and Nafion forming a P-F bond as seen from the X-ray Photoelectron Spectroscopy (XPS). However, when measuring electrical properties of the Nafion coated on BP, the BP would still degrade quickly. However, when Nafion was selectively coated on BP surface, it was found that the BP wasn’t only improved stability, but also shown excellent electrical properties, such as on-off ratio of 104 and the hole mobility of 117.38 cm2V-1S-1.
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